A power battery heating method and system, and a vehicle electric drive device

Abstract

The application provides a power battery heating method and system and a vehicle electric drive device. The method comprises the following steps: correcting a d-axis voltage amplitude limit value corresponding to a d-axis voltage amplitude limit value initial instruction according to a power battery heating environment, to obtain a d-axis voltage amplitude correction limit value; correcting a d-axis current limit value corresponding to a d-axis current limit value initial instruction, to obtain a d-axis current correction limit value; predicting a d-axis current to obtain a d-axis current prediction value; obtaining a d-axis voltage amplitude limit value real-time instruction through the d-axis voltage amplitude correction limit value, the d-axis current correction limit value and the d-axis current prediction value; providing positive and negative sudden change voltage to the d-axis based on the d-axis voltage amplitude limit value real-time instruction, and generating a pulse current by using a d-axis inductance, so as to heat the power battery according to the pulse current. The application can periodically charge and discharge the power battery by generating the pulse current, so as to heat the power battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a power battery heating method and system, and a vehicle electric drive device. Background Technology

[0002] Currently, most new energy vehicles use lithium-ion batteries as energy storage devices. The performance of lithium-ion batteries is greatly affected by temperature. In low-temperature environments, the performance of lithium-ion batteries will deteriorate significantly and the discharge capacity will decrease. Therefore, a solution for heating lithium-ion batteries is needed. Summary of the Invention

[0003] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a power battery heating method and system, and a vehicle electric drive device, to solve the problem of how to quickly heat the power battery.

[0004] To achieve the above and other related objectives, the present invention provides a method for heating a power battery, comprising the following steps:

[0005] Obtain the initial command for the motor direct-axis voltage amplitude limit and the initial command for the motor direct-axis current limit, which are generated in advance or in real time.

[0006] The motor direct-axis voltage amplitude limit corresponding to the initial command of the motor direct-axis voltage amplitude limit is corrected according to the power battery heating environment to obtain the corrected limit of the motor direct-axis voltage amplitude; and the motor direct-axis current limit corresponding to the initial command of the motor direct-axis current limit is corrected according to the power battery heating environment to obtain the corrected limit of the motor direct-axis current.

[0007] The current of the motor direct shaft is predicted to obtain the predicted value of the motor direct shaft current.

[0008] The initial command for the motor direct-axis voltage amplitude limit is adjusted using the motor direct-axis voltage amplitude correction limit, the motor direct-axis current correction limit, and the predicted value of the motor direct-axis current to obtain the real-time command for the motor direct-axis voltage amplitude limit.

[0009] Based on the real-time command of the motor direct shaft voltage amplitude limit, a voltage with sudden positive and negative changes is provided to the motor direct shaft, and a pulse current is generated by the motor direct shaft inductance to heat the power battery according to the pulse current.

[0010] In one embodiment of the present invention, the process of predicting the motor direct shaft current to obtain the predicted value of the motor direct shaft current includes:

[0011] Obtain the motor direct-axis inductance value and the motor direct-axis voltage amplitude during the current power battery heating cycle;

[0012] The motor direct-axis inductance value and the motor direct-axis voltage amplitude during the current power battery heating cycle are input into the current calculation equation to predict the change in motor direct-axis current and the motor direct-axis current value during the next power battery heating cycle; wherein, the current calculation equation includes: In the formula, Ud represents the amplitude of the motor direct-axis voltage during the current power battery heating cycle, and L d This indicates the direct-axis inductance value of the motor. t represents the change in the direct-axis current of the motor, and t represents the time of the power battery heating cycle.

[0013] In one embodiment of the present invention, the process of predicting the motor direct shaft current to obtain the predicted value of the motor direct shaft current includes:

[0014] Calculate the current difference between the motor direct-axis current value in the current power battery heating cycle and the motor direct-axis current value in the previous power battery heating cycle, and predict the motor direct-axis current value in the next power battery heating cycle based on the current difference.

[0015] In one embodiment of the present invention, after obtaining the predicted value of the direct-axis current of the motor, the method further includes:

[0016] The predicted value of the motor direct-axis current is compared with the motor direct-axis current limit corresponding to the initial command of the motor direct-axis current limit. When the predicted value of the motor direct-axis current is greater than the motor direct-axis current limit, the motor direct-axis voltage amplitude limit corresponding to the initial command of the motor direct-axis voltage amplitude limit is reversed to provide overcurrent protection for the motor through the reverse action of the voltage.

[0017] Alternatively, the predicted value of the motor direct-axis current is compared with the motor direct-axis current correction limit. When the predicted value of the motor direct-axis current is greater than the motor direct-axis current correction limit, the motor direct-axis voltage amplitude correction limit is reversed to provide overcurrent protection for the motor through the reverse action of the voltage.

[0018] In one embodiment of the present invention, the process of providing a voltage with abrupt positive and negative changes to the direct shaft of the motor based on the real-time command of the direct shaft voltage amplitude limit includes:

[0019] In response to the real-time command of the motor direct-axis voltage amplitude limit, the motor torque equation is obtained;

[0020] Based on the motor torque equation, after controlling the motor quadrature axis current and motor quadrature axis voltage to zero respectively, a voltage with abrupt positive and negative changes is provided to the motor direct axis.

[0021] In one embodiment of the present invention, when a voltage with abrupt positive and negative changes is provided to the direct shaft of the motor, the waveform of the voltage includes: square wave, sine wave, triangular wave or trapezoidal wave.

[0022] In one embodiment of the present invention, before obtaining the pre-generated or real-time generated initial command for the motor direct-axis voltage amplitude limit and the initial command for the motor direct-axis current limit, the method further includes:

[0023] Check if the motor is faulty, and check if the motor controller is faulty;

[0024] If the motor is fault-free, the motor controller normally receives the power battery heating command sent from the outside, and the motor controller is fault-free internally, then it obtains the initial command of the motor direct axis voltage amplitude limit and the initial command of the motor direct axis current limit generated in advance or in real time.

[0025] If the motor malfunctions, the motor controller cannot properly receive the power battery heating command sent from the outside, and / or there is a fault inside the motor controller, then the acquisition of the pre-generated or real-time initial command for the motor direct-axis voltage amplitude limit and the initial command for the motor direct-axis current limit will be stopped.

[0026] In one embodiment of the present invention, the generation process of the initial command for the motor direct-axis voltage amplitude limit and the initial command for the motor direct-axis current limit includes:

[0027] Based on the status of the motor, the status of the motor controller, and the status of the power battery, the initial command for the motor direct-axis voltage amplitude limit and the initial command for the motor direct-axis current limit are generated in advance or in real time.

[0028] The present invention also provides a power battery heating system, comprising:

[0029] The initial instruction module is used to obtain the initial instructions for the motor direct-axis voltage amplitude limit and the initial instructions for the motor direct-axis current limit, which are generated in advance or in real time.

[0030] The correction module is used to correct the motor direct-axis voltage amplitude limit corresponding to the initial command of the motor direct-axis voltage amplitude limit according to the power battery heating environment, so as to obtain the corrected limit of the motor direct-axis voltage amplitude; and to correct the motor direct-axis current limit corresponding to the initial command of the motor direct-axis current limit according to the power battery heating environment, so as to obtain the corrected limit of the motor direct-axis current.

[0031] The current prediction module is used to predict the current of the motor direct shaft and obtain the predicted value of the motor direct shaft current.

[0032] The instruction adjustment module is used to adjust the initial instruction of the motor direct-axis voltage amplitude limit by means of the motor direct-axis voltage amplitude correction limit, the motor direct-axis current correction limit, and the motor direct-axis current prediction value, so as to obtain the real-time instruction of the motor direct-axis voltage amplitude limit;

[0033] The power battery heating module is used to provide a voltage with sudden positive and negative changes to the motor direct shaft according to the real-time command of the motor direct shaft voltage amplitude limit, and to generate a pulse current using the motor direct shaft inductance, so as to heat the power battery according to the pulse current.

[0034] The present invention also provides a vehicle electric drive device for performing the power battery heating method as described in any one of the above.

[0035] As described above, the present invention provides a power battery heating method and system, and a vehicle electric drive device, which has the following beneficial effects: The present invention obtains a pre-generated or real-time initial command for the motor direct-axis voltage amplitude limit and an initial command for the motor direct-axis current limit; then, it corrects the motor direct-axis voltage amplitude limit corresponding to the initial command for the motor direct-axis voltage amplitude limit according to the power battery heating environment to obtain a corrected limit for the motor direct-axis voltage amplitude; and, it corrects the motor direct-axis current limit corresponding to the initial command for the motor direct-axis current limit according to the power battery heating environment to obtain a corrected limit for the motor direct-axis current; then, it predicts the current of the motor direct-axis to obtain a predicted value for the motor direct-axis current; then, it adjusts the initial command for the motor direct-axis voltage amplitude limit using the corrected limit for the motor direct-axis voltage amplitude, the corrected limit for the motor direct-axis current, and the predicted value for the motor direct-axis current to obtain a real-time command for the motor direct-axis voltage amplitude limit; finally, based on the real-time command for the motor direct-axis voltage amplitude limit, it provides a voltage with abrupt positive and negative changes to the motor direct-axis and uses the motor direct-axis inductance to generate a pulse current to heat the power battery according to the pulse current. Therefore, this invention generates pulsed current, enabling the power battery to be periodically charged and discharged, thereby heating the battery. Furthermore, by combining the predicted value of the motor's direct-axis current with a real-time command to adjust the motor's direct-axis voltage amplitude limit, this invention can protect the motor and prevent transient overcurrent in the motor's direct-axis current, which could lead to motor malfunction. In addition, before providing a voltage with abrupt positive and negative changes to the motor's direct-axis, this invention can control the motor's quadrature-axis current and voltage to zero according to the motor torque equation, thereby avoiding the generation of motor torque and reducing damage to the power devices in the motor controller. Attached Figure Description

[0036] Figure 1 This is a schematic flowchart of a power battery heating method provided in one embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram illustrating the relationship between temperature and time during heating of a power battery according to an embodiment of the present invention;

[0038] Figure 3 This is a schematic flowchart of a power battery heating method provided in another embodiment of the present invention;

[0039] Figure 4 This is a schematic diagram of the circuit connection for heating a power battery according to an embodiment of the present invention.

[0040] Figure 5 This is a schematic diagram of the direct-axis voltage waveform of a motor provided in one embodiment of the present invention;

[0041] Figure 6 This is a schematic diagram of the circuit connection when the power battery is discharging, according to an embodiment of the present invention.

[0042] Figure 7 This is a schematic diagram of the circuit connection for charging a power battery according to an embodiment of the present invention;

[0043] Figure 8 This is a schematic diagram of the hardware structure of a power battery heating system provided in one embodiment of the present invention. Detailed Implementation

[0044] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0045] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0046] Current power battery heating technologies primarily utilize the vehicle's thermal management system, employing coolant heated by other devices (such as PTC thermistors and electric drive systems) to heat the battery. This indirect heating method suffers from a slow heating rate. Another approach involves directly heating the battery by generating pulsed current through the electric drive system. This utilizes the motor's inductance to produce pulsed current, which then generates heat through the battery's internal resistance. However, this approach is prone to triggering overcurrent, overtemperature, torque generation, and noise in the electric drive system. While some shortcomings can be mitigated by modifying modulation algorithms, such as by shutting down power devices to allow current freewheeling back to the battery, this optimization process can easily damage inverter power devices, especially SiC MOS power modules. SiC devices have high body diode resistance and low overcurrent capacity during freewheeling, making them susceptible to overheating and damage. Furthermore, modifying modulation algorithms requires significant software changes, preventing the reuse of commonly used motor control algorithms like SVPWM (Space Vector Pulse Width Modulation), increasing development complexity and reducing functional stability. In view of the above problems or defects, this embodiment provides a power battery heating method and system to solve the above problems or defects.

[0047] Specifically, in one exemplary embodiment, Figure 1 A schematic flowchart of a power battery heating method according to an embodiment of the present invention is shown. Figure 1 As shown, this embodiment provides a method for heating a power battery, which includes the following steps:

[0048] S110, Obtain the pre-generated or real-time generated initial command for the motor direct-axis voltage amplitude limit and the initial command for the motor direct-axis current limit. As an example, in this embodiment, the generation process of the initial command for the motor direct-axis voltage amplitude limit and the initial command for the motor direct-axis current limit includes: generating the initial command for the motor direct-axis voltage amplitude limit and the initial command for the motor direct-axis current limit in advance or in real-time according to the state of the motor, the state of the motor controller, and the state of the power battery. Specifically, the initial command for the motor direct-axis voltage amplitude limit and the initial command for the motor direct-axis current limit can be generated using preset values, or they can be generated according to the state of the three-electric system; for example, setting the motor direct-axis voltage amplitude limit based on the bus voltage magnitude, and then generating the corresponding command to obtain the initial command for the motor direct-axis voltage amplitude limit. In this embodiment, the three-electric system includes, but is not limited to, the motor, the motor controller, and the power battery in a new energy vehicle. In this embodiment or other embodiments, the motor direct axis can also be referred to as the d-axis, and the motor quadrature axis can be referred to as the q-axis; the motor can constitute or be referred to as an electric drive device, and the motor controller can also be constituted by an inverter.

[0049] S120: Based on the power battery heating environment, the motor direct-axis voltage amplitude limit corresponding to the initial command for the motor direct-axis voltage amplitude limit is corrected to obtain the corrected motor direct-axis voltage amplitude limit; and based on the power battery heating environment, the motor direct-axis current limit corresponding to the initial command for the motor direct-axis current limit is corrected to obtain the corrected motor direct-axis current limit. As an example, in this embodiment, the power battery heating environment includes, but is not limited to: external water temperature, external voltage, motor controller temperature, motor controller voltage, power battery temperature, power battery voltage, stator temperature in the motor, rotor temperature in the motor, and inverter power device temperature in the motor controller.

[0050] S130, predict the current of the motor direct shaft to obtain the predicted value of the motor direct shaft current;

[0051] S140, by adjusting the initial command of the motor direct-axis voltage amplitude limit through the motor direct-axis voltage amplitude correction limit, the motor direct-axis current correction limit, and the motor direct-axis current prediction value, the real-time command of the motor direct-axis voltage amplitude limit is obtained;

[0052] S150, based on the real-time command of the motor direct shaft voltage amplitude limit, provides a voltage with abrupt positive and negative changes to the motor direct shaft, and uses the motor direct shaft inductance to generate a pulse current to heat the power battery according to the pulse current. As an example, when this embodiment provides a voltage with abrupt positive and negative changes to the motor direct shaft, the voltage waveform includes, but is not limited to: square wave, sine wave, triangle wave, or trapezoidal wave.

[0053] Therefore, this embodiment can generate pulsed current to periodically charge and discharge the power battery, thereby heating the battery. Furthermore, by combining the predicted value of the motor direct-axis current with the real-time command to adjust the motor direct-axis voltage amplitude limit, this embodiment can protect the motor and prevent transient overcurrent in the motor direct-axis current, which could lead to motor failure. In addition, before providing a voltage change of positive or negative to the motor direct-axis, this embodiment can control the motor quadrature-axis current and voltage to zero according to the motor torque equation, thereby avoiding the generation of motor torque and reducing damage to the power devices in the motor controller. The relationship between temperature and time during power battery heating provided in this embodiment is as follows: Figure 2 As shown. Therefore, the power battery heating solution provided in this embodiment can achieve a heating speed of more than 2 cycles per minute. Compared with other existing heating solutions, it improves heating efficiency and saves heating time. In this embodiment, the circuit connection when the power battery is discharging is as follows. Figure 6 As shown, the circuit connection for charging the power battery is as follows: Figure 7 As shown.

[0054] During the power battery heating process, due to changes in motor temperature and physical characteristics such as inductor saturation, the resistance of the motor windings and the magnitude of the motor direct-axis inductance will change, leading to transient overcurrent in the phase current. Therefore, it is necessary to control the motor direct-axis current to avoid overcurrent. Specifically, in an exemplary embodiment, the process of predicting the motor direct-axis current to obtain the predicted value of the motor direct-axis current may include: obtaining the motor direct-axis inductance value and the motor direct-axis voltage amplitude in the current power battery heating cycle; inputting the motor direct-axis inductance value and the motor direct-axis voltage amplitude in the current power battery heating cycle into the current calculation equation to predict the change in motor direct-axis current and the motor direct-axis current value in the next power battery heating cycle; wherein, the current calculation equation includes: In the formula, Ud represents the amplitude of the motor direct-axis voltage during the current power battery heating cycle, and L d This indicates the direct-axis inductance value of the motor. The value represents the change in the motor direct-axis current, and t represents the time of the power battery heating cycle. Furthermore, after obtaining the predicted value of the motor direct-axis current, this embodiment may further include: comparing the predicted value of the motor direct-axis current with the motor direct-axis current limit corresponding to the initial command of the motor direct-axis current limit; and when the predicted value of the motor direct-axis current is greater than the motor direct-axis current limit, reversing the motor direct-axis voltage amplitude limit corresponding to the initial command of the motor direct-axis voltage amplitude limit, so as to provide overcurrent protection for the motor through the reverse action of the voltage.

[0055] According to the above description, in another exemplary embodiment, the process of predicting the direct-axis current of the motor to obtain the predicted value of the direct-axis current may further include: calculating the current difference between the direct-axis current value of the motor in the current power battery heating cycle and the direct-axis current value of the motor in the previous power battery heating cycle, and predicting the direct-axis current value of the motor in the next power battery heating cycle based on the current difference. Furthermore, after obtaining the predicted value of the direct-axis current, this embodiment may further include: comparing the predicted value of the direct-axis current with a correction limit for the direct-axis current, and when the predicted value of the direct-axis current is greater than the correction limit, reversing the correction limit for the direct-axis voltage amplitude to provide overcurrent protection for the motor through the reverse action of the voltage.

[0056] Therefore, since there is a delay when the motor controller generates the control voltage, this embodiment can predict the current of the motor direct shaft and then control the current according to the predicted current to avoid overcurrent in the motor direct shaft, thereby protecting the motor.

[0057] In an exemplary embodiment, the process of providing a voltage with abrupt positive and negative changes to the direct shaft of a motor based on a real-time command specifying the direct shaft voltage amplitude limit may include: obtaining a motor torque equation in response to the real-time command specifying the direct shaft voltage amplitude limit; and, based on the motor torque equation, controlling the motor quadrature-axis current and motor quadrature-axis voltage to zero respectively, providing a voltage with abrupt positive and negative changes to the direct shaft of the motor. As an example, when this embodiment provides a voltage with abrupt positive and negative changes to the direct shaft of the motor, the voltage waveform may include, but is not limited to, a square wave, a sine wave, a triangular wave, or a trapezoidal wave. As an example, when this embodiment follows... Figure 4 When the circuit connection shown is used for heating the power battery, the motor is in a state of either a lower three-transistor short circuit or an upper three-transistor short circuit. In this state, current flows inside the motor and does not enter the battery. Therefore, the use of the voltage vector corresponding to the lower or upper three-transistor short circuit should be minimized as much as possible. The effective value of the given motor direct-axis voltage amplitude Ud needs to be as large as possible. Therefore, in this embodiment, a square wave can be selected as the most effective waveform corresponding to the direct-axis voltage command. Figure 4 In the circuit connection shown, the lower three transistors can be composed of MOSFETs U2, V2, and W2; the upper three transistors can be composed of MOSFETs U1, V1, and W1. The voltage vector for short-circuiting the lower three transistors can be set to 000, and the voltage vector for short-circuiting the upper three transistors can be set to 111.

[0058] In an exemplary embodiment, before obtaining the pre-generated or real-time generated initial commands for the motor direct-axis voltage amplitude limit and the motor direct-axis current limit, this embodiment may further include:

[0059] Check if the motor is faulty, and check if the motor controller is faulty;

[0060] If the motor is fault-free, the motor controller can normally receive the power battery heating command sent from the outside, and if the motor controller is fault-free, it can obtain the initial command of the motor direct axis voltage amplitude limit and the initial command of the motor direct axis current limit generated in advance or in real time.

[0061] If the motor malfunctions and the motor controller cannot properly receive the power battery heating command sent from the outside, and / or if there is a fault inside the motor controller, then the acquisition of the pre-generated or real-time initial command for the motor direct-axis voltage amplitude limit and the initial command for the motor direct-axis current limit will be stopped.

[0062] Therefore, before generating the initial command for the motor direct-axis voltage amplitude limit and the initial command for the motor direct-axis current limit, this embodiment can check whether the function can be enabled normally. The enabling conditions include, but are not limited to: 1) receiving the command to enable the function from the upper-level controller; 2) no fault inside the motor controller; 3) no fault inside the motor.

[0063] In another exemplary embodiment of the present invention, Figure 3 A schematic flowchart of a power battery heating method according to an embodiment of the present invention is shown. Figure 3 As shown, this embodiment provides a method for heating a power battery, which includes the following steps:

[0064] Implementation Step A: It is necessary to check whether the function can be enabled normally. The enabling conditions include, but are not limited to: 1) receiving the instruction to enable the function from the upper controller; 2) no internal faults in the motor controller; 3) no internal faults in the motor.

[0065] Implementation Step B: After the function is enabled normally, it is necessary to generate d-axis voltage amplitude limit and current limit commands. According to the motor torque equation, to avoid torque, the q-axis current needs to be controlled to 0. Therefore, the q-axis voltage should be 0, and the q-axis current should be controlled to 0. Simultaneously, given an alternating positive and negative d-axis voltage, an alternating current is generated using the motor's d-axis inductance. Since the d-axis voltage is always given through a modulation algorithm, there is no situation where all six bridge arms are completely turned off. Therefore, the current will not freewheel through the body diode to the bus battery, and the power module will not be damaged. The d-axis voltage amplitude limit and current limit commands can use preset values ​​or be generated according to the state of the three-electric system, such as setting the d-axis voltage amplitude limit based on the bus voltage. In this embodiment, the three-electric system includes, but is not limited to, the motor, motor controller, and power battery in a new energy vehicle.

[0066] Implementation Step C: Adjust the real-time d-axis voltage amplitude limit command. In the motor control modulation algorithm, when the voltage vector is 000 or 111, the motor is in a state of short circuit in the lower three transistors or the upper three transistors. In this state, current flows inside the motor and does not enter the battery. Therefore, the use of these two vectors should be minimized as much as possible. Thus, the effective value of the given d-axis voltage amplitude Ud needs to be as large as possible. Therefore, the most effective waveform for the d-axis voltage amplitude limit command is a square wave. The waveform of the d-axis voltage amplitude Ud is as follows: Figure 5 As shown. During operation, due to changes in motor temperature and physical characteristics such as inductor saturation, the resistance of the motor windings and the magnitude of the d-axis inductance will change, leading to transient overcurrent in the phase current. Therefore, it is necessary to control the d-axis current to prevent overcurrent. One method to control the d-axis current is to reverse the d-axis voltage amplitude limit command value when an excessive d-axis current is detected. Through the reverse action of the voltage, the d-axis current will decrease rapidly.

[0067] Implementation Step D: Adjust the d-axis voltage amplitude limit and d-axis current limit by considering multiple factors. Changes in external conditions, such as water temperature and voltage variations, can cause malfunctions in the electric drive system or battery system, such as overheating or overvoltage. Therefore, the d-axis voltage amplitude limit and d-axis current monitoring threshold need to be dynamically adjusted by integrating various temperature and voltage information, including but not limited to water temperature, stator temperature, rotor temperature, and power module temperature.

[0068] Implementation Step E: To achieve better current control, the magnitude of the d-axis current was predicted. Since there is a delay between calculating and generating the final control voltage, a current prediction module is needed to predict the d-axis current. The prediction method can be: predicting the current of the next cycle based on the current difference between the previous two cycles and implementing control strategies in advance. Alternatively, the prediction method can be: using the d-axis inductance value L from pre-calibrated motor parameters. d ,pass To predict the current change and the current value in the next cycle.

[0069] In the power battery heating scheme provided in this embodiment, the relationship between temperature and time during power battery heating is as follows: Figure 2 As shown. Therefore, the power battery heating solution provided in this embodiment can achieve a heating speed of more than 2 cycles per minute. Compared with other existing heating solutions, it improves heating efficiency and saves heating time. In this embodiment, the circuit connection when the power battery is discharging is as follows. Figure 6 As shown, the circuit connection for charging the power battery is as follows: Figure 7 As shown, this embodiment generates pulsed current to periodically charge and discharge the power battery, thereby heating it. Furthermore, by combining the predicted value of the motor direct-axis current with a real-time command to adjust the motor direct-axis voltage amplitude limit, this embodiment protects the motor and prevents transient overcurrent in the motor direct-axis current, which could lead to motor failure. In addition, before providing a voltage change of positive or negative to the motor direct-axis, this embodiment can control the motor quadrature-axis current and voltage to zero according to the motor torque equation, thereby avoiding the generation of motor torque and reducing damage to the power devices in the motor controller.

[0070] In summary, this invention provides a power battery heating method. This method involves acquiring a pre-generated or real-time initial command for the motor direct-axis voltage amplitude limit and an initial command for the motor direct-axis current limit; then, correcting the motor direct-axis voltage amplitude limit corresponding to the initial command based on the power battery heating environment to obtain a corrected motor direct-axis voltage amplitude limit; further, correcting the motor direct-axis current limit corresponding to the initial command based on the power battery heating environment to obtain a corrected motor direct-axis current limit; predicting the motor direct-axis current to obtain a predicted motor direct-axis current value; adjusting the initial command for the motor direct-axis voltage amplitude limit using the corrected motor direct-axis voltage amplitude limit, the corrected motor direct-axis current limit, and the predicted motor direct-axis current value to obtain a real-time command for the motor direct-axis voltage amplitude limit; finally, based on the real-time command for the motor direct-axis voltage amplitude limit, providing a voltage with abrupt positive and negative changes to the motor direct-axis, and generating a pulse current using the motor direct-axis inductance to heat the power battery according to the pulse current. Therefore, this method generates pulsed current to periodically charge and discharge the power battery, thereby heating it. Furthermore, by combining the predicted direct-axis current value with a real-time command to adjust the direct-axis voltage amplitude limit, this method protects the motor and prevents transient overcurrent in the direct-axis current, which could lead to motor failure. In addition, before providing abrupt positive and negative voltage changes to the direct-axis, this method can control the quadrature-axis current and voltage to zero according to the motor torque equation, thus avoiding the generation of motor torque and reducing damage to the power devices in the motor controller.

[0071] like Figure 8 As shown, in another exemplary embodiment of the present invention, this embodiment provides a power battery heating system, including:

[0072] The initial instruction module 810 is used to obtain the initial instruction for the motor direct-axis voltage amplitude limit and the initial instruction for the motor direct-axis current limit, which are generated in advance or in real time. As an example, in this embodiment, the generation process of the initial instruction for the motor direct-axis voltage amplitude limit and the initial instruction for the motor direct-axis current limit includes: generating the initial instruction for the motor direct-axis voltage amplitude limit and the initial instruction for the motor direct-axis current limit in advance or in real time according to the state of the motor, the state of the motor controller, and the state of the power battery. Specifically, the initial instruction for the motor direct-axis voltage amplitude limit and the initial instruction for the motor direct-axis current limit can be generated using preset values, or they can be generated according to the state of the three-electric system; for example, setting the motor direct-axis voltage amplitude limit based on the bus voltage magnitude, and then generating the corresponding instruction to obtain the initial instruction for the motor direct-axis voltage amplitude limit. In this embodiment, the three-electric system includes, but is not limited to, the motor, the motor controller, and the power battery in a new energy vehicle. In this embodiment or other embodiments, the motor direct axis can also be referred to as the d-axis, and the motor quadrature axis can be referred to as the q-axis; the motor can constitute or be referred to as an electric drive device, and the motor controller can also be constituted by an inverter.

[0073] The correction module 820 is used to correct the motor direct-axis voltage amplitude limit corresponding to the initial command of the motor direct-axis voltage amplitude limit based on the power battery heating environment, to obtain a corrected motor direct-axis voltage amplitude limit; and to correct the motor direct-axis current limit corresponding to the initial command of the motor direct-axis current limit based on the power battery heating environment, to obtain a corrected motor direct-axis current limit. As an example, in this embodiment, the power battery heating environment includes, but is not limited to: external water temperature, external voltage, motor controller temperature, motor controller voltage, power battery temperature, power battery voltage, stator temperature in the motor, rotor temperature in the motor, and inverter power device temperature in the motor controller.

[0074] The current prediction module 830 is used to predict the current of the motor direct shaft and obtain the predicted value of the motor direct shaft current.

[0075] The instruction adjustment module 840 is used to adjust the initial instruction of the motor direct-axis voltage amplitude limit by means of the motor direct-axis voltage amplitude correction limit, the motor direct-axis current correction limit, and the motor direct-axis current prediction value, so as to obtain the real-time instruction of the motor direct-axis voltage amplitude limit.

[0076] The power battery heating module 850 is used to provide a voltage with sudden positive and negative changes to the motor direct shaft according to the real-time command of the motor direct shaft voltage amplitude limit, and to generate a pulse current using the inductance of the motor direct shaft to heat the power battery according to the pulse current. As an example, when the voltage with sudden positive and negative changes is provided to the motor direct shaft in this embodiment, the voltage waveform includes, but is not limited to: square wave, sine wave, triangle wave, or trapezoidal wave.

[0077] Therefore, this embodiment can generate pulsed current to periodically charge and discharge the power battery, thereby heating the battery. Furthermore, by combining the predicted value of the motor direct-axis current with the real-time command to adjust the motor direct-axis voltage amplitude limit, this embodiment can protect the motor and prevent transient overcurrent in the motor direct-axis current, which could lead to motor failure. In addition, before providing a voltage change of positive or negative to the motor direct-axis, this embodiment can control the motor quadrature-axis current and voltage to zero according to the motor torque equation, thereby avoiding the generation of motor torque and reducing damage to the power devices in the motor controller. The relationship between temperature and time during power battery heating provided in this embodiment is as follows: Figure 2 As shown. Therefore, the power battery heating solution provided in this embodiment can achieve a heating speed of more than 2 cycles per minute. Compared with other existing heating solutions, it improves heating efficiency and saves heating time. In this embodiment, the circuit connection when the power battery is discharging is as follows. Figure 6 As shown, the circuit connection for charging the power battery is as follows: Figure 7 As shown.

[0078] During the power battery heating process, due to changes in motor temperature and physical characteristics such as inductor saturation, the resistance of the motor windings and the magnitude of the motor direct-axis inductance will change, leading to transient overcurrent in the phase current. Therefore, it is necessary to control the motor direct-axis current to avoid overcurrent. Specifically, in an exemplary embodiment, the process of predicting the motor direct-axis current to obtain the predicted value of the motor direct-axis current may include: obtaining the motor direct-axis inductance value and the motor direct-axis voltage amplitude in the current power battery heating cycle; inputting the motor direct-axis inductance value and the motor direct-axis voltage amplitude in the current power battery heating cycle into the current calculation equation to predict the change in motor direct-axis current and the motor direct-axis current value in the next power battery heating cycle; wherein, the current calculation equation includes: In the formula, Ud represents the amplitude of the motor direct-axis voltage during the current power battery heating cycle, and L d This indicates the direct-axis inductance value of the motor. The value represents the change in the motor direct-axis current, and t represents the time of the power battery heating cycle. Furthermore, after obtaining the predicted value of the motor direct-axis current, this embodiment may further include: comparing the predicted value of the motor direct-axis current with the motor direct-axis current limit corresponding to the initial command of the motor direct-axis current limit; and when the predicted value of the motor direct-axis current is greater than the motor direct-axis current limit, reversing the motor direct-axis voltage amplitude limit corresponding to the initial command of the motor direct-axis voltage amplitude limit, so as to provide overcurrent protection for the motor through the reverse action of the voltage.

[0079] According to the above description, in another exemplary embodiment, the process of predicting the direct-axis current of the motor to obtain the predicted value of the direct-axis current may further include: calculating the current difference between the direct-axis current value of the motor in the current power battery heating cycle and the direct-axis current value of the motor in the previous power battery heating cycle, and predicting the direct-axis current value of the motor in the next power battery heating cycle based on the current difference. Furthermore, after obtaining the predicted value of the direct-axis current, this embodiment may further include: comparing the predicted value of the direct-axis current with a correction limit for the direct-axis current, and when the predicted value of the direct-axis current is greater than the correction limit, reversing the correction limit for the direct-axis voltage amplitude to provide overcurrent protection for the motor through the reverse action of the voltage.

[0080] Therefore, since there is a delay when the motor controller generates the control voltage, this embodiment can predict the current of the motor direct shaft and then control the current according to the predicted current to avoid overcurrent in the motor direct shaft, thereby protecting the motor.

[0081] In an exemplary embodiment, the process of providing a voltage with abrupt positive and negative changes to the direct shaft of a motor based on a real-time command specifying the direct shaft voltage amplitude limit may include: obtaining a motor torque equation in response to the real-time command specifying the direct shaft voltage amplitude limit; and, based on the motor torque equation, controlling the motor quadrature-axis current and motor quadrature-axis voltage to zero respectively, providing a voltage with abrupt positive and negative changes to the direct shaft of the motor. As an example, when this embodiment provides a voltage with abrupt positive and negative changes to the direct shaft of the motor, the voltage waveform may include, but is not limited to, a square wave, a sine wave, a triangular wave, or a trapezoidal wave. As an example, when this embodiment follows... Figure 4 When the circuit connection shown is used for heating the power battery, the motor is in a state of either a lower three-transistor short circuit or an upper three-transistor short circuit. In this state, current flows inside the motor and does not enter the battery. Therefore, the use of the voltage vector corresponding to the lower or upper three-transistor short circuit should be minimized as much as possible. The effective value of the given motor direct-axis voltage amplitude Ud needs to be as large as possible. Therefore, in this embodiment, a square wave can be selected as the most effective waveform corresponding to the direct-axis voltage command. Figure 4 In the circuit connection shown, the lower three transistors can be composed of MOSFETs U2, V2, and W2; the upper three transistors can be composed of MOSFETs U1, V1, and W1. The voltage vector for short-circuiting the lower three transistors can be set to 000, and the voltage vector for short-circuiting the upper three transistors can be set to 111.

[0082] In an exemplary embodiment, before obtaining the pre-generated or real-time generated initial commands for the motor direct-axis voltage amplitude limit and the motor direct-axis current limit, this embodiment may further include:

[0083] Check if the motor is faulty, and check if the motor controller is faulty;

[0084] If the motor is fault-free, the motor controller can normally receive the power battery heating command sent from the outside, and if the motor controller is fault-free, it can obtain the initial command of the motor direct axis voltage amplitude limit and the initial command of the motor direct axis current limit generated in advance or in real time.

[0085] If the motor malfunctions and the motor controller cannot properly receive the power battery heating command sent from the outside, and / or if there is a fault inside the motor controller, then the acquisition of the pre-generated or real-time initial command for the motor direct-axis voltage amplitude limit and the initial command for the motor direct-axis current limit will be stopped.

[0086] Therefore, before generating the initial command for the motor direct-axis voltage amplitude limit and the initial command for the motor direct-axis current limit, this embodiment can check whether the function can be enabled normally. The enabling conditions include, but are not limited to: 1) receiving the command to enable the function from the upper-level controller; 2) no fault inside the motor controller; 3) no fault inside the motor.

[0087] In another exemplary embodiment of the present invention, this embodiment provides a power battery heating system for performing the following steps:

[0088] Implementation Step A: It is necessary to check whether the function can be enabled normally. The enabling conditions include, but are not limited to: 1) receiving the instruction to enable the function from the upper controller; 2) no internal faults in the motor controller; 3) no internal faults in the motor.

[0089] Implementation Step B: After the function is enabled normally, it is necessary to generate d-axis voltage amplitude limit and current limit commands. According to the motor torque equation, to avoid torque, the q-axis current needs to be controlled to 0. Therefore, the q-axis voltage should be 0, and the q-axis current should be controlled to 0. Simultaneously, given an alternating positive and negative d-axis voltage, an alternating current is generated using the motor's d-axis inductance. Since the d-axis voltage is always given through a modulation algorithm, there is no situation where all six bridge arms are completely turned off. Therefore, the current will not freewheel through the body diode to the bus battery, and the power module will not be damaged. The d-axis voltage amplitude limit and current limit commands can use preset values ​​or be generated according to the state of the three-electric system, such as setting the d-axis voltage amplitude limit based on the bus voltage. In this embodiment, the three-electric system includes, but is not limited to, the motor, motor controller, and power battery in a new energy vehicle.

[0090] Implementation Step C: Adjust the real-time d-axis voltage amplitude limit command. In the motor control modulation algorithm, when the voltage vector is 000 or 111, the motor is in a state of short circuit in the lower three transistors or the upper three transistors. In this state, current flows inside the motor and does not enter the battery. Therefore, the use of these two vectors should be minimized as much as possible. Thus, the effective value of the given d-axis voltage amplitude Ud needs to be as large as possible. Therefore, the most effective waveform for the d-axis voltage amplitude limit command is a square wave. The waveform of the d-axis voltage amplitude Ud is as follows: Figure 5 As shown. During operation, due to changes in motor temperature and physical characteristics such as inductor saturation, the resistance of the motor windings and the magnitude of the d-axis inductance will change, leading to transient overcurrent in the phase current. Therefore, it is necessary to control the d-axis current to prevent overcurrent. One method to control the d-axis current is to reverse the d-axis voltage amplitude limit command value when an excessive d-axis current is detected. Through the reverse action of the voltage, the d-axis current will decrease rapidly.

[0091] Implementation Step D: Adjust the d-axis voltage amplitude limit and d-axis current limit by considering multiple factors. Changes in external conditions, such as water temperature and voltage variations, can cause malfunctions in the electric drive system or battery system, such as overheating or overvoltage. Therefore, the d-axis voltage amplitude limit and d-axis current monitoring threshold need to be dynamically adjusted by integrating various temperature and voltage information, including but not limited to water temperature, stator temperature, rotor temperature, and power module temperature.

[0092] Implementation Step E: To achieve better current control, the magnitude of the d-axis current was predicted. Since there is a delay between calculating and generating the final control voltage, a current prediction module is needed to predict the d-axis current. The prediction method can be: predicting the current of the next cycle based on the current difference between the previous two cycles and implementing control strategies in advance. Alternatively, the prediction method can be: using the d-axis inductance value L from pre-calibrated motor parameters. d ,pass To predict the current change and the current value in the next cycle.

[0093] In the power battery heating scheme provided in this embodiment, the relationship between temperature and time during power battery heating is as follows: Figure 2 As shown. Therefore, the power battery heating solution provided in this embodiment can achieve a heating speed of more than 2 cycles per minute. Compared with other existing heating solutions, it improves heating efficiency and saves heating time. In this embodiment, the circuit connection when the power battery is discharging is as follows. Figure 6 As shown, the circuit connection for charging the power battery is as follows: Figure 7As shown, this embodiment generates pulsed current to periodically charge and discharge the power battery, thereby heating it. Furthermore, by combining the predicted value of the motor direct-axis current with a real-time command to adjust the motor direct-axis voltage amplitude limit, this embodiment protects the motor and prevents transient overcurrent in the motor direct-axis current, which could lead to motor failure. In addition, before providing a voltage change of positive or negative to the motor direct-axis, this embodiment can control the motor quadrature-axis current and voltage to zero according to the motor torque equation, thereby avoiding the generation of motor torque and reducing damage to the power devices in the motor controller.

[0094] In summary, this invention provides a power battery heating system. It acquires pre-generated or real-time initial commands for the motor direct-axis voltage amplitude limit and the motor direct-axis current limit; then, based on the power battery heating environment, it corrects the motor direct-axis voltage amplitude limit corresponding to the initial command to obtain a corrected motor direct-axis voltage amplitude limit; and further, it corrects the motor direct-axis current limit corresponding to the initial command to obtain a corrected motor direct-axis current limit; then, it predicts the motor direct-axis current to obtain a predicted motor direct-axis current value; finally, based on the real-time command, it provides a voltage with abrupt positive and negative changes to the motor direct-axis and generates a pulse current using the motor direct-axis inductance to heat the power battery. Therefore, this system generates pulsed current to periodically charge and discharge the power battery, thereby heating it. Furthermore, by combining the predicted direct-axis current value with real-time commands to adjust the direct-axis voltage amplitude limit, the system protects the motor and prevents transient overcurrent in the direct-axis current, which could lead to motor malfunction. In addition, before supplying a voltage with sudden positive or negative changes to the direct-axis, the system can control the quadrature-axis current and voltage to zero according to the motor torque equation, thus avoiding the generation of motor torque and reducing damage to the power devices in the motor controller.

[0095] It should be noted that the power battery heating system provided in the above embodiments and the power battery heating method provided in the above embodiments belong to the same concept. The specific way in which each module performs its operation has been described in detail in the method embodiments, and will not be repeated here. In practical applications, the power battery heating system provided in the above embodiments can be assigned to different functional modules as needed, that is, the internal structure of the system can be divided into different functional modules to complete all or part of the functions described above. This is not a limitation here.

[0096] In another embodiment of the present invention, a vehicle electric drive device is also provided for performing the power battery heating method as described in some or one of the above embodiments. As an example, the vehicle electric drive device in this embodiment may be composed of an electric motor. It should be noted that the vehicle electric drive device provided in this embodiment and the power battery heating method provided in the above embodiments belong to the same concept. The specific manner in which the vehicle electric drive device performs its operation has been described in detail in the above method embodiments, and the corresponding technical effects can be referred to in the above method embodiments. This embodiment will not be repeated here.

[0097] It should be noted that when the above embodiments process relevant data (such as d-axis voltage amplitude limit instructions and d-axis current limit instructions, power battery heating environment data, etc.), such as collecting, storing, using, processing, transmitting, providing, disclosing, deleting, etc., it is done with or with the user's consent. For example, the power battery heating environment data is obtained with the user's knowledge and consent; or it is provided voluntarily by the user after reading the relevant instructions; or it is actively authorized / provided / uploaded by the user when using some or all of the functions described in the above embodiments; or it is obtained through other means / paths with or with the user's consent.

[0098] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for heating a power battery, characterized in that, Includes the following steps: Obtain the initial command for the motor direct-axis voltage amplitude limit and the initial command for the motor direct-axis current limit, which are generated in advance or in real time. The motor direct-axis voltage amplitude limit corresponding to the initial command of the motor direct-axis voltage amplitude limit is corrected according to the power battery heating environment to obtain the corrected limit of the motor direct-axis voltage amplitude. Furthermore, the motor direct-axis current limit corresponding to the initial command of the motor direct-axis current limit is corrected according to the power battery heating environment to obtain the corrected motor direct-axis current limit. The current of the motor direct shaft is predicted to obtain the predicted value of the motor direct shaft current. The initial command for the motor direct-axis voltage amplitude limit is adjusted using the motor direct-axis voltage amplitude correction limit, the motor direct-axis current correction limit, and the predicted value of the motor direct-axis current to obtain the real-time command for the motor direct-axis voltage amplitude limit. Based on the real-time command of the motor direct shaft voltage amplitude limit, a voltage with sudden positive and negative changes is provided to the motor direct shaft, and a pulse current is generated by the motor direct shaft inductance to heat the power battery according to the pulse current.

2. The power battery heating method according to claim 1, characterized in that, The process of predicting the direct-axis current of a motor to obtain the predicted value of the direct-axis current includes: Obtain the motor direct-axis inductance value and the motor direct-axis voltage amplitude during the current power battery heating cycle; The motor direct-axis inductance value and the motor direct-axis voltage amplitude during the current power battery heating cycle are input into the current calculation equation to predict the change in motor direct-axis current and the motor direct-axis current value during the next power battery heating cycle; wherein, the current calculation equation includes: In the formula, Ud represents the amplitude of the motor direct-axis voltage during the current power battery heating cycle, and L d This indicates the direct-axis inductance value of the motor. t represents the change in the direct-axis current of the motor, and t represents the time of the power battery heating cycle.

3. The power battery heating method according to claim 1, characterized in that, The process of predicting the direct-axis current of a motor to obtain the predicted value of the direct-axis current includes: Calculate the current difference between the motor direct-axis current value in the current power battery heating cycle and the motor direct-axis current value in the previous power battery heating cycle, and predict the motor direct-axis current value in the next power battery heating cycle based on the current difference.

4. The power battery heating method according to claim 2 or 3, characterized in that, After obtaining the predicted value of the direct-axis current of the motor, the method further includes: The predicted value of the motor direct-axis current is compared with the motor direct-axis current limit corresponding to the initial command of the motor direct-axis current limit. When the predicted value of the motor direct-axis current is greater than the motor direct-axis current limit, the motor direct-axis voltage amplitude limit corresponding to the initial command of the motor direct-axis voltage amplitude limit is reversed to provide overcurrent protection for the motor through the reverse action of the voltage. Alternatively, the predicted value of the motor direct-axis current is compared with the motor direct-axis current correction limit. When the predicted value of the motor direct-axis current is greater than the motor direct-axis current correction limit, the motor direct-axis voltage amplitude correction limit is reversed to provide overcurrent protection for the motor through the reverse action of the voltage.

5. The power battery heating method according to claim 1, characterized in that, Based on the real-time command of the motor direct-axis voltage amplitude limit, the process of providing a voltage with sudden positive and negative changes to the motor direct-axis includes: In response to the real-time command of the motor direct-axis voltage amplitude limit, the motor torque equation is obtained; Based on the motor torque equation, after controlling the motor quadrature axis current and motor quadrature axis voltage to zero respectively, a voltage with abrupt positive and negative changes is provided to the motor direct axis.

6. The power battery heating method according to claim 1 or 5, characterized in that, When a voltage with abrupt positive and negative changes is supplied to the direct shaft of a motor, the voltage waveform includes: square wave, sine wave, triangle wave, or trapezoidal wave.

7. The power battery heating method according to claim 1, characterized in that, Before obtaining the pre-generated or real-time initial commands for the motor direct-axis voltage amplitude limit and the motor direct-axis current limit, the method further includes: Check if the motor is faulty, and check if the motor controller is faulty; If the motor is fault-free, the motor controller normally receives the power battery heating command sent from the outside, and the motor controller is fault-free internally, then it obtains the initial command of the motor direct axis voltage amplitude limit and the initial command of the motor direct axis current limit generated in advance or in real time. If the motor malfunctions, the motor controller cannot properly receive the power battery heating command sent from the outside, and / or there is a fault inside the motor controller, then the acquisition of the pre-generated or real-time initial command for the motor direct-axis voltage amplitude limit and the initial command for the motor direct-axis current limit will be stopped.

8. The power battery heating method according to claim 1 or 7, characterized in that, The generation process of the initial command for the motor direct-axis voltage amplitude limit and the initial command for the motor direct-axis current limit includes: Based on the status of the motor, the status of the motor controller, and the status of the power battery, the initial command for the motor direct-axis voltage amplitude limit and the initial command for the motor direct-axis current limit are generated in advance or in real time.

9. A power battery heating system, characterized in that, Including: The initial instruction module is used to obtain the initial instructions for the motor direct-axis voltage amplitude limit and the initial instructions for the motor direct-axis current limit, which are generated in advance or in real time. The correction module is used to correct the motor direct-axis voltage amplitude limit corresponding to the initial command of the motor direct-axis voltage amplitude limit according to the power battery heating environment, so as to obtain the corrected limit of the motor direct-axis voltage amplitude. Furthermore, the motor direct-axis current limit corresponding to the initial command of the motor direct-axis current limit is corrected according to the power battery heating environment to obtain the corrected motor direct-axis current limit. The current prediction module is used to predict the current of the motor direct shaft and obtain the predicted value of the motor direct shaft current. The instruction adjustment module is used to adjust the initial instruction of the motor direct-axis voltage amplitude limit by means of the motor direct-axis voltage amplitude correction limit, the motor direct-axis current correction limit, and the motor direct-axis current prediction value, so as to obtain the real-time instruction of the motor direct-axis voltage amplitude limit; The power battery heating module is used to provide a voltage with sudden positive and negative changes to the motor direct shaft according to the real-time command of the motor direct shaft voltage amplitude limit, and to generate a pulse current using the motor direct shaft inductance, so as to heat the power battery according to the pulse current.

10. A vehicle electric drive device, characterized in that, The vehicle electric drive unit is used to perform the power battery heating method as described in any one of claims 1 to 7.

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